Determine the nature of dark matter using Milky Way stellar streams

Determine the fundamental nature of dark matter by leveraging constraints from Milky Way stellar streams that have been discovered and characterized with Gaia astrometry and spectroscopy, which provide sensitive probes of the Galactic gravitational field and dark matter substructure.

Background

The review emphasizes that stellar streams—tidal debris from disrupted globular clusters and dwarf galaxies—are exceptionally sensitive tracers of the Milky Way’s gravitational potential, including its dark matter component. Because streams retain coherent dynamical structure over gigayear timescales, their morphology and kinematics encode information about the mass distribution and substructure of the dark halo.

Gaia’s all-sky astrometry and photometry have catalyzed a step change in the number, quality, and characterization of known streams, enabling measurements of orbits, density variations, and perturbations that are predicted to arise from dark-matter subhalos. These measurements position stellar streams as a leading avenue to probe dark matter microphysics and halo structure, thereby addressing the long-standing question of dark matter’s nature.

References

The Milky Way stellar streams are poised to answer one of the major open questions in both physics and astrophysics---the nature of dark matter.

— Stellar Streams in the Gaia Era  (2405.19410 - Bonaca et al., 2024) in Section 1, Introduction

Perhaps the most important open question, and the one that ties this review most directly back to the dark matter problem introduced in Section~\ref{sec:dmproblem}, is how stream signatures connect to the fundamental nature of dark matter.

— Dark Matter in the Galaxy: Insights from the Dynamics of Stellar Streams  (2610.22202 - Ayaz et al., 15 Oct 2026) in Section 5.5, “Small-Scale Structure and the Nature of Dark Matter”

It remains an open challenge to determine whether current and future stream samples can robustly distinguish between these scenarios.

— Dark Matter in the Galaxy: Insights from the Dynamics of Stellar Streams  (2610.22202 - Ayaz et al., 15 Oct 2026) in Section 5.5, “Small-Scale Structure and the Nature of Dark Matter”